"config.exs not found" on running first line of Configuration section
I set up an Ubuntu virtual machine on Digital Ocean, upgraded to 20.04.2 LTS, to test Mobilizon. The release setup guide's Configuration section has this line:
sudo -u mobilizon ./bin/mobilizon_ctl instance gen --output /etc/mobilizon/config.exs --output-psql /tmp/setup_db.psql
After I run this, I get the following error followed by the process continuing:
!!! /etc/mobilizon/config.exs not found! Please ensure it exists and that MOBILIZON_CONFIG_PATH is unset or points to an existing file What domain will your instance use? (e.g mobilizon.org) 
Did I do something wrong in the setup, or does this always happen?